Observation of the 0<SUP>++</SUP> gluonium ground state in antiproton annihilations at rest

by Ugo GASTALDI (INFN Laboratori Nazionali di Legnaro & CERN - EP)

Friday 5 May 2000, 14:00 → 14:15 Europe/Zurich

TH Auditorium (CERN)

The signals of three isoscalar scalar states, f₀(980), f₀ (1400) and f₀ (1500), clearly visible in antiproton annihilations at rest with protons and neutrons (measured at LEAR and in bubble chamber experiments recently revisited), are reviewed and the values of the production times decay branching ratios available in the literature are discussed critically in comparison with the data. The three structures have relatively narrow apparent widths, respectively of the order of 50, 200 and 100 MeV. The ratio of the decay branching ratios into KKbar and into two pions exceeds 0.5 for both f₀ (1400) and f₀ (1500). The branching ratio for the ss decays of f₀ (1400) exceeds that for the two pion decays by a factor larger than 10. This factor is instead of the order of 1 for f₀ (1500). The ratios of the decay branching ratios into two pions, KKbar and hh of f₀ (1400) and f₀ (1500) exclude ideal mixing for the scalar nonet. The dominant ss decay of f₀ (1400), which has too low energy to decay into hh' points at a dominant gg component. The absence of a f₀ (1400) signal in gg interactions and in Kaon interactions with nucleons, and its presence in central production support the conclusion that f₀ (1400) is mostly made of glue.

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